(CNN) -- Sens. John McCain and Barack Obama began to formally prepare for their first debate only this week, but their campaigns began negotiations months ago with the Commission on Presidential Debates.

A commission official said the independent, nonpartisan group first submitted its proposal to the campaigns several months ago, allowing time for each to make suggestions on everything from time limits to the debate format.

Both campaigns largely agreed to the organization's recommendations, the official said.

Among them is a major new feature: In the first and third presidential debates, there will be a five-minute "discussion" period following each candidate's answer to a question. The idea is to promote more freewheeling back-and-forth between the candidates, the commission official said.

The negotiations appear to lack the same degree of contention that marked the discussions between the campaigns of President Bush and Sen. John Kerry in 2004. After reportedly heated talks, the campaigns emerged with a 32-page agreement that set out the rules for the debates with great specificity, down to details such as the temperature of the hall, what kind of paper could be used to take notes and who could stand in the wings.

Many of those details have yet to be worked out this year, a commission member said.

But the Obama and McCain campaigns did request some changes. The commission had originally wanted domestic issues to be the topic of the first debate, saving foreign policy for the third and final debate. (The second presidential debate, a town-hall format that fields questions exclusively from the audience, can cover any topic.)

Don't Miss

However, both campaigns wanted foreign policy up first, a decision the commission agreed to before the financial crisis erupted last week on Wall Street.

The New York Times also reported Sunday that the McCain campaign sought to limit the time for freewheeling discussion in the vice presidential debate, scheduled for October 6.

Advisers to McCain's running mate, Sarah Palin, were reportedly worried that format could put the Alaska governor -- a relatively inexperienced debater -- on the defensive most the evening. Watch how Palin seems to be shielded »

Officials with the debate commission say most of the proposed rules were left in place for both the presidential and vice presidential debates -- from how the moderators will allot the 90 minutes to how the candidates will be positioned on stage.

Debate commission officials say the first and third presidential debates will feature largely the same format. The moderators -- PBS' Jim Lehrer for the first and CBS' Bob Schieffer for the third -- will divide the debate into approximately eight 10-minute segments. The moderator will introduce each segment with an issue and give each candidate two minutes to respond.

Then comes the five-minute discussion period, when direct exchanges between the candidates will occur.

Unlike 2004, there will be no lights or buzzers indicating to viewers that time has expired, but the limits will still be strictly enforced.

Obama and McCain will be standing at podiums in the first debate and be seated around a table in the third.

The second matchup will feature a town-hall format in front of an audience of undecided voters identified by the Gallup Organization.

NBC News' Tom Brokaw will select questions from the audience before the program and allow each candidate a two-minute response, during which each will be able to move around the stage. Brokaw will then be given an additional minute for any follow-up questions.

But in a presidential campaign that has stretched longer than any other, it remains to be seen if the debates will be a game-changer.

"Debates are usually more important when candidates are not as well known. This campaign, however, has been longer than train smoke," said Alex Castellanos, a Republican strategist and CNN contributor. "Both these candidates have been campaigning for years, so voters have gotten to know them."